1. Field of the Invention
The invention relates to a control circuit to wake up or turn on a computer via a peripheral device. More particularly, the invention relates to a control circuit and a method to wake up or turn on a computer while it is in a standby or off state without using panel switch.
2. Description of the Related Art
A pure mechanical touch-type panel switch is used to turn on/off a power supply in a conventional personal computer (PC) or a workstation with a microprocessor as a kernel. The power supply includes an alternating current (ac) source such as a domestic electricity supply. When the power source is open, there is no power supplied to the power supply of the system, so that the system is in an off state. On the contrary, when the power source is switched to a close state, an ac current is supplied to the power supply of the system. The power supply can thus supply various direct (dc), typically positive/negative (+/-) 5V and positive/negative (+/-) 12V to turn on the computer system. This mechanical type power switch has to be switched manually to turn on/off the computer. Without an operator, the system can not be turned on or off.
A series of Macintosh personal computers developed by Apple Computer Inc., Cupertino, Calif. uses a power-on key on the keyboard to turn on/off the computer system. This is a very handy way for turning on/off the computer system.
The Intel Corporation, Santa Clara, Calif. also proposed an ATX specification of a personal computer. In the ATX specification, a mechanical on/off switch is not used any more as the power supply to directly control system. Instead, the ATX specification uses a circuit in an internal control chip to manage and control the power supply of the computer system. That is, a software control concept is implanted. Various types of switching on/off methods can be applied to control a computer system without being restricted by a mechanically switch which can only set and control the computer in an on or an off state.
For example, the version 2.01 of the ATX specification comprises a spare power source 5VSB which supplies a dc voltage of 5V and a maximum current of 0.7 A. The spare power source 5VSB can thus drive a basic power source control circuit of the computer system under the off state. Functions to advantage the operation can be achieved by setting the control circuit. For example, the system can be preset to be turned on automatically at night. Therefore, an international facsimile can be sent during a period of time which has a cheaper calling rate without the presence of an operator. Moreover, while no operator is available or present, the system can be turned on by an incoming event such as a signal received by a modem. The system can thus receive the incoming message or document automatically.
However, the above power source on/off control is restricted to only turn on/off the system. To control the computer system while it is still in an on state is not disclosed. The Intel, Microsoft, and Toshiba later disclose an advanced configuration and power interface (ACPI) interface to specify four standby states for a computer system during a working and off state. The state of the computer is determined according the working load of the computer to save energy. According to the saved energy, the state of the computer may comprise S1 to S4 states. In the S1 state, the central processing unit (CPU) clock is stopped. The S2 state is a "suspend to RAM" state, the S3 state is a "suspend to disk state", and the S4 state is a soft off state. When the system is in the "suspended to RAM" state, apart from the real-time clock, the other clock pulse has been stopped. The CPU and other circuits are stopped without being supplied by any clock pulse. If a user want to wake up the system, he/she has to press a panel switch to notice the computer back to an operation state. Meanwhile, the keyboard controller and the infrared controller (or the serial port) can not function to wake up the system since they both have stopped working.
FIG. 1 shows diagram illustrating the connection relationship between a peripheral device 11 and a peripheral device controller 12 of a computer system. When the state of the computer system is in the "suspended to RAM" state, the peripheral device controller 12 has stopped functioning. Therefore, the task to wake up the system can not be done by the peripheral device 11. If a user wants to wake up the system, he/she has to press a panel switch to generate and send a signal PENAL_SW_IN to chipset 13 on a mother board 10. Thus, when the system is in a standby state, the computer can only be woken up through the panel switch. While the system is in an off state, it is impossible to be turned up via the peripheral device 11.
Thus, according to the conventional method, no matter if the computer is in a standby or an off state, only the current existent switching method, for example, by a panel switch, a keyboard, a mouse, an alarm, a modem, or a network, can achieve the wake-up or turn-on task. The task can not be achieved by way of a peripheral device.